Yes, a better antenna would help...
Serveral years ago, I bought a Motorola broadband signal booster (part #484095-001-00) to solve a weak signal problem with my cable TV reception. The problem subsequently having been resolved, the signal booster sat in a closet. Today I decided to try it between the rabbit ear antenna I am using and the RTLSDR dongle. The results were quite dramatic. The manufacturer claims a 15 db gain between 52 and 1001 Mhz, and I can concur that I am seeing every bit of those results. Weak stations are coming in much stronger, and I am discovering new stations that were non existent before. Strong stations are now all at -10 db. Definetely worth the price ($35 at Best Buy), as this is a rugged device meant for outdoor installation. A cheaper alternative might be an indoor model, such this RCA 10 db amplifier ($15). And I am quite keen to try this Winegard HDA-200, which claims a 24 db gain.
For the uninitiated, a 15 db gain is a 32 fold increase in signal strength (10 raised to the power of 15/10), while a 24 db gain is a 251 fold increase in signal strength (10 raised to the power of 24/10). I will advise how it goes, and yes, I have another dongle still in the package if I blow this one out with too much signal!
By the way, with all this weight hanging off the RTLSDR dongle, it would be wise to get a USB hub with a fairly long cable, so that the dongle can lay flat on a surface rather than struggle to stay attached to a PC or laptop USB port. If you have ever opened one up, you have seen it would not take much for the USB connector to break off the circuit board.